Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/34—Heterocyclic compounds having nitrogen in the ring
  • C08K5/3412—Heterocyclic compounds having nitrogen in the ring having one nitrogen atom in the ring
  • C08K5/3432—Six-membered rings
  • C08K5/3435—Piperidines
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/20—Carboxylic acid amides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/49—Phosphorus-containing compounds
  • C08K5/51—Phosphorus bound to oxygen
  • C08K5/52—Phosphorus bound to oxygen only
  • C08K5/527—Cyclic esters

Definitions

• This invention relates to compositions of propylene polymers suitable for high energy radiation treatment and to articles manufactured from such polymer compositions.
• Propylene polymers and specifically those of a substantial crystalline content have been applied to many new uses, which uses have required that the polymer be processed or treated in a particular manner.
• propylene polymers generally have the contact clarity, heat distortion resistance and low chemical reactivity required by manufacturers of medical single-use items such as syringes, forceps, surgical clamps and various instrument trays, etc. used in the operating room. Obviously, before any such articles can be safely used, it is required that it be sterilized.
• Ethylene oxide has the sterilizing effectiveness needed by these same manufacturers, and has been regarded in the past as generally safe. Recently, however, ethylene oxide has come under increasing scrutiny by the authorities, since it is believed to be a mutagen and possibly a carcinogen. Acceptable limits of residual ethylene oxide and its by-products have, therefore, been lowered. In addition, the cost of ethylene oxide is rising and the sterilizing costs (because of a 14-day holding requirement and the individual batch testing requirement) are becoming non-competitive.
• High energy radiation leaves no residue and has a dose-related sterilization rate which permits immediate release upon certification of the dose.
• radiation especially gamma radiation, damages the polymer in that it causes either embrittlement or discoloration or both of these effects occur simultaneously.
• the discoloration is attributable to the use of phenolic antioxidants in the compositions to prevent or minimize the radiation-induced degradation of the polymer. Even worse discoloration is obtained with additive systems containing phenolic antioxidants and a thiodipropionic ester synergist.
• European Pat. No. 7736 teaches that if certain hindered amines are incorporated into a polyolefin, such as propylene homopolymer, there is obtained an improvement in resistance to discoloration which occurs as a result of gamma radiation.
• the patent discourages the use of phenolic antioxidants in the composition since they are likely to cause aggravated discoloration.
• the absence of an antioxidant will result in processing problems during molding, and sterilized articles manufactured from the composition will lack the required shelf life.
• a high energy radiation sterilizable propylene polymer composition comprising a propylene polymer resin containing:
• the propylene polymer resin can be a propylene homopolymer, a random copolymer of propylene and ethylene containing from about 0.5 to about 6 wt %, preferably from about 1 to about 5 wt %, polymerized ethylene or a mixture of the homopolymer and copolymer.
• the propylene polymer resin can also contain other polymers in minor proportions such as ethylene polymers and, in particular, linear low density polyethylene (LLDPE) which are copolymers of ethylene and at least one C 4 -C 18 alpha-olefin and which have densities in the range from about 0.910 to about 0.935 gm/cc.
• LLDPE linear low density polyethylene
• the alpha-olefin comonomer contains from 4 to 8 carbon atoms per molecule.
• suitable comonomers are butene-1, pentene-1, hexene-1, 4-methyl-pentene-1, heptene-1, octene-1 and mixtures thereof such as butene-1/hexene-1 and butene-1/octene-1, etc.
• LLDPE resins can be produced by any of the recently introduced catalytic processes using vapor, solution or slurry techniques at low to medium pressures or high pressure catalytic polymerization in autoclave or tubular reactors.
• the resin preferably has a density of from about 0.910 to about 0.920. A variety of suitable resins are commercially available within the required density.
• a particularly preferred propylene polymer resin is one comprised from about 0 to about 50 wt % of propylene homopolymer, from about 40 to about 97 wt % of a random propylene/ethylene copolymer and from about 3 to about 10 wt % of a linear low density polyethylene.
• Upon radiation treatment there occurs simultaneously a certain amount of scission as well as of cross-linking of the polymer molecules resulting in a desirous improvement in the strength properties of the resin, e.g. in crush resistance.
• the preferred hindered amines are those wherein R 1 is methyl, x and y are both 2 and n is between 5-20 . Such compounds are commercially available. These amines are suitably added to provide a concentration in the polymer between about 0.1 and about 0.4.
• the R 2 and R 3 alkyl groups of the di(substituted)pentaerythritol diphosphite preferably contain from 12 to 18 carbon atoms and are suitable selected from lauryl, palmitic or stearyl groups.
• the preferred concentration of the diphosphite is between about 0.05 and about 0.2 wt % based on the polymer weight.
• the preferred hindered phenolic antioxidant is one where R 4 is t-butyl and x and y are both 2 and its concentration in the polymer is preferably maintained from about 0.03 to about 0.15 wt %.
• a catalyst residue neutralizer is usually required when the polymer resin has been prepared by polymerization in the presence of one of the newly developed, highly active catalysts, since the use of such catalysts obviates the need for a separate polymer deashing step.
• the neutralizer is typically added in quantities between about 0.02 and about 0.20 wt % based on the polymer weight.
• additives include coloring agents, lubricants, clarifying and/or nucleating agents, melt flow modifying agents and others.
• coloring agents lubricants, clarifying and/or nucleating agents, melt flow modifying agents and others.
• clarifying and/or nucleating agents e.g., talc, kaolin
• the resin blend can be processed into molded articles by various techniques such as blow molding and injection molding.
• the composition is especially suitable for the production if disposable hypodermic syringes, medicine vials and other radiation sterilizable articles used for medical purposes.
• the composition is also used with advantage in food packaging applications such as retort packaging where radiation treatment is used to prevent unwanted growth of microorganisms.
• the high energy radiation is conveniently provided by a cobalt 60 source.
• Other radiation treatment can be used such as high energy x-rays or high energy electrons (beta radiation).
• radiation dosages that can be applied range up to about 5 megarads.
• an article of manufacture such as a syringe can be effectively sterilized by applying 1.5 megarads under gamma radiation.
• compositions were prepared from the compounds described below in the amounts shown in Table I.
• the propylene homopolymer was an undeashed resin prepared in the presence of a high-activity magnesium chloride-supported titanium chloride catalyst and an organoaluminum cocatalyst.
• the polymer of Example 1 had a melt flow rate of about 12, while that of Examples 2-6 had an initial melt flow rate of about 4.
• the random propylene polymer component was an undeashed copolymer containing 1.8 wt % polymerized ethylene on an average.
• the melt flow of the polymer was about 9 g/10 min at 230° C. and 2.16 kg load.
• Tinuvin®622 LD (CIBA-GEIGY), a dimethylsuccinate polymer with 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol,
• NAUGARD®XL-1 which is a hindered phenolic antioxidant and metal deactivator chemically defined as 2,2'-oxamidobis-ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,
• Lupersol®101 which is a di-t-butylperoxide used as a melt flow medifier to obtain a resin of controlled rheology
• Tensile bar specimens (21/2" ⁇ 1/2" ⁇ 60 mil) were prepared from each of these blends and were then subjected to gamma radiation with doses of 0, 1.5, 2,5-2.7 and 3.5-3.7 megarads respectively employing a cobalt 60 source.
• Tensile bar specimens were prepared and irradiated with doses of 0, 1.5, 3 and 5 Mrad employing a cobalt 60 source.
• the melt flow rate and the tensile properties were measured on the initially treated samples and after aging.
• the Yellowness Index (ASTM D-1708) was determined on initially treated and aged samples, of which half had been in daylight and the other half in a dark environment as would occur when the end products are packed and stored in shipping cartons. The test results are shown in Table III.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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Cited By (24)

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• 1985
  • 1985-12-10 US US06/807,139 patent/US4666959A/en not_active Expired - Lifetime
• 1986
  • 1986-11-19 CA CA000523305A patent/CA1277063C/en not_active Expired - Fee Related
  • 1986-12-09 NO NO864958A patent/NO176803C/no not_active IP Right Cessation
  • 1986-12-09 DE DE8686309585T patent/DE3686939T2/de not_active Expired - Fee Related
  • 1986-12-09 EP EP86309585A patent/EP0228837B1/de not_active Expired - Lifetime
  • 1986-12-10 JP JP61292672A patent/JPS62138544A/ja active Pending

Patent Citations (4)

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